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Diffstat (limited to 'bfd/doc/targets.texi')
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diff --git a/bfd/doc/targets.texi b/bfd/doc/targets.texi new file mode 100644 index 0000000..542de04 --- /dev/null +++ b/bfd/doc/targets.texi @@ -0,0 +1,563 @@ +@section Targets + + +@strong{Description}@* +Each port of BFD to a different machine requires the creation +of a target back end. All the back end provides to the root +part of BFD is a structure containing pointers to functions +which perform certain low level operations on files. BFD +translates the applications's requests through a pointer into +calls to the back end routines. + +When a file is opened with @code{bfd_openr}, its format and +target are unknown. BFD uses various mechanisms to determine +how to interpret the file. The operations performed are: + +@itemize @bullet + +@item +Create a BFD by calling the internal routine +@code{_bfd_new_bfd}, then call @code{bfd_find_target} with the +target string supplied to @code{bfd_openr} and the new BFD pointer. + +@item +If a null target string was provided to @code{bfd_find_target}, +look up the environment variable @code{GNUTARGET} and use +that as the target string. + +@item +If the target string is still @code{NULL}, or the target string is +@code{default}, then use the first item in the target vector +as the target type, and set @code{target_defaulted} in the BFD to +cause @code{bfd_check_format} to loop through all the targets. +@xref{bfd_target}. @xref{Formats}. + +@item +Otherwise, inspect the elements in the target vector +one by one, until a match on target name is found. When found, +use it. + +@item +Otherwise return the error @code{bfd_error_invalid_target} to +@code{bfd_openr}. + +@item +@code{bfd_openr} attempts to open the file using +@code{bfd_open_file}, and returns the BFD. +@end itemize +Once the BFD has been opened and the target selected, the file +format may be determined. This is done by calling +@code{bfd_check_format} on the BFD with a suggested format. +If @code{target_defaulted} has been set, each possible target +type is tried to see if it recognizes the specified format. +@code{bfd_check_format} returns @code{TRUE} when the caller guesses right. +@menu +* bfd_target:: +@end menu + +@node bfd_target, , Targets, Targets + +@subsection bfd_target + + +@strong{Description}@* +This structure contains everything that BFD knows about a +target. It includes things like its byte order, name, and which +routines to call to do various operations. + +Every BFD points to a target structure with its @code{xvec} +member. + +The macros below are used to dispatch to functions through the +@code{bfd_target} vector. They are used in a number of macros further +down in @file{bfd.h}, and are also used when calling various +routines by hand inside the BFD implementation. The @var{arglist} +argument must be parenthesized; it contains all the arguments +to the called function. + +They make the documentation (more) unpleasant to read, so if +someone wants to fix this and not break the above, please do. +@example +#define BFD_SEND(bfd, message, arglist) \ + ((*((bfd)->xvec->message)) arglist) + +#ifdef DEBUG_BFD_SEND +#undef BFD_SEND +#define BFD_SEND(bfd, message, arglist) \ + (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \ + ((*((bfd)->xvec->message)) arglist) : \ + (bfd_assert (__FILE__,__LINE__), NULL)) +#endif +@end example +For operations which index on the BFD format: +@example +#define BFD_SEND_FMT(bfd, message, arglist) \ + (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist) + +#ifdef DEBUG_BFD_SEND +#undef BFD_SEND_FMT +#define BFD_SEND_FMT(bfd, message, arglist) \ + (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \ + (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist) : \ + (bfd_assert (__FILE__,__LINE__), NULL)) +#endif + +@end example +This is the structure which defines the type of BFD this is. The +@code{xvec} member of the struct @code{bfd} itself points here. Each +module that implements access to a different target under BFD, +defines one of these. + +FIXME, these names should be rationalised with the names of +the entry points which call them. Too bad we can't have one +macro to define them both! +@example +enum bfd_flavour +@{ + bfd_target_unknown_flavour, + bfd_target_aout_flavour, + bfd_target_coff_flavour, + bfd_target_ecoff_flavour, + bfd_target_xcoff_flavour, + bfd_target_elf_flavour, + bfd_target_ieee_flavour, + bfd_target_nlm_flavour, + bfd_target_oasys_flavour, + bfd_target_tekhex_flavour, + bfd_target_srec_flavour, + bfd_target_verilog_flavour, + bfd_target_ihex_flavour, + bfd_target_som_flavour, + bfd_target_os9k_flavour, + bfd_target_versados_flavour, + bfd_target_msdos_flavour, + bfd_target_ovax_flavour, + bfd_target_evax_flavour, + bfd_target_mmo_flavour, + bfd_target_mach_o_flavour, + bfd_target_pef_flavour, + bfd_target_pef_xlib_flavour, + bfd_target_sym_flavour +@}; + +enum bfd_endian @{ BFD_ENDIAN_BIG, BFD_ENDIAN_LITTLE, BFD_ENDIAN_UNKNOWN @}; + +/* Forward declaration. */ +typedef struct bfd_link_info _bfd_link_info; + +typedef struct bfd_target +@{ + /* Identifies the kind of target, e.g., SunOS4, Ultrix, etc. */ + char *name; + + /* The "flavour" of a back end is a general indication about + the contents of a file. */ + enum bfd_flavour flavour; + + /* The order of bytes within the data area of a file. */ + enum bfd_endian byteorder; + + /* The order of bytes within the header parts of a file. */ + enum bfd_endian header_byteorder; + + /* A mask of all the flags which an executable may have set - + from the set @code{BFD_NO_FLAGS}, @code{HAS_RELOC}, ...@code{D_PAGED}. */ + flagword object_flags; + + /* A mask of all the flags which a section may have set - from + the set @code{SEC_NO_FLAGS}, @code{SEC_ALLOC}, ...@code{SET_NEVER_LOAD}. */ + flagword section_flags; + + /* The character normally found at the front of a symbol. + (if any), perhaps `_'. */ + char symbol_leading_char; + + /* The pad character for file names within an archive header. */ + char ar_pad_char; + + /* The maximum number of characters in an archive header. */ + unsigned short ar_max_namelen; + + /* Entries for byte swapping for data. These are different from the + other entry points, since they don't take a BFD as the first argument. + Certain other handlers could do the same. */ + bfd_uint64_t (*bfd_getx64) (const void *); + bfd_int64_t (*bfd_getx_signed_64) (const void *); + void (*bfd_putx64) (bfd_uint64_t, void *); + bfd_vma (*bfd_getx32) (const void *); + bfd_signed_vma (*bfd_getx_signed_32) (const void *); + void (*bfd_putx32) (bfd_vma, void *); + bfd_vma (*bfd_getx16) (const void *); + bfd_signed_vma (*bfd_getx_signed_16) (const void *); + void (*bfd_putx16) (bfd_vma, void *); + + /* Byte swapping for the headers. */ + bfd_uint64_t (*bfd_h_getx64) (const void *); + bfd_int64_t (*bfd_h_getx_signed_64) (const void *); + void (*bfd_h_putx64) (bfd_uint64_t, void *); + bfd_vma (*bfd_h_getx32) (const void *); + bfd_signed_vma (*bfd_h_getx_signed_32) (const void *); + void (*bfd_h_putx32) (bfd_vma, void *); + bfd_vma (*bfd_h_getx16) (const void *); + bfd_signed_vma (*bfd_h_getx_signed_16) (const void *); + void (*bfd_h_putx16) (bfd_vma, void *); + + /* Format dependent routines: these are vectors of entry points + within the target vector structure, one for each format to check. */ + + /* Check the format of a file being read. Return a @code{bfd_target *} or zero. */ + const struct bfd_target *(*_bfd_check_format[bfd_type_end]) (bfd *); + + /* Set the format of a file being written. */ + bfd_boolean (*_bfd_set_format[bfd_type_end]) (bfd *); + + /* Write cached information into a file being written, at @code{bfd_close}. */ + bfd_boolean (*_bfd_write_contents[bfd_type_end]) (bfd *); + +@end example +The general target vector. These vectors are initialized using the +BFD_JUMP_TABLE macros. +@example + + /* Generic entry points. */ +#define BFD_JUMP_TABLE_GENERIC(NAME) \ + NAME##_close_and_cleanup, \ + NAME##_bfd_free_cached_info, \ + NAME##_new_section_hook, \ + NAME##_get_section_contents, \ + NAME##_get_section_contents_in_window + + /* Called when the BFD is being closed to do any necessary cleanup. */ + bfd_boolean (*_close_and_cleanup) (bfd *); + /* Ask the BFD to free all cached information. */ + bfd_boolean (*_bfd_free_cached_info) (bfd *); + /* Called when a new section is created. */ + bfd_boolean (*_new_section_hook) (bfd *, sec_ptr); + /* Read the contents of a section. */ + bfd_boolean (*_bfd_get_section_contents) + (bfd *, sec_ptr, void *, file_ptr, bfd_size_type); + bfd_boolean (*_bfd_get_section_contents_in_window) + (bfd *, sec_ptr, bfd_window *, file_ptr, bfd_size_type); + + /* Entry points to copy private data. */ +#define BFD_JUMP_TABLE_COPY(NAME) \ + NAME##_bfd_copy_private_bfd_data, \ + NAME##_bfd_merge_private_bfd_data, \ + _bfd_generic_init_private_section_data, \ + NAME##_bfd_copy_private_section_data, \ + NAME##_bfd_copy_private_symbol_data, \ + NAME##_bfd_copy_private_header_data, \ + NAME##_bfd_set_private_flags, \ + NAME##_bfd_print_private_bfd_data + + /* Called to copy BFD general private data from one object file + to another. */ + bfd_boolean (*_bfd_copy_private_bfd_data) (bfd *, bfd *); + /* Called to merge BFD general private data from one object file + to a common output file when linking. */ + bfd_boolean (*_bfd_merge_private_bfd_data) (bfd *, bfd *); + /* Called to initialize BFD private section data from one object file + to another. */ +#define bfd_init_private_section_data(ibfd, isec, obfd, osec, link_info) \ + BFD_SEND (obfd, _bfd_init_private_section_data, (ibfd, isec, obfd, osec, link_info)) + bfd_boolean (*_bfd_init_private_section_data) + (bfd *, sec_ptr, bfd *, sec_ptr, struct bfd_link_info *); + /* Called to copy BFD private section data from one object file + to another. */ + bfd_boolean (*_bfd_copy_private_section_data) + (bfd *, sec_ptr, bfd *, sec_ptr); + /* Called to copy BFD private symbol data from one symbol + to another. */ + bfd_boolean (*_bfd_copy_private_symbol_data) + (bfd *, asymbol *, bfd *, asymbol *); + /* Called to copy BFD private header data from one object file + to another. */ + bfd_boolean (*_bfd_copy_private_header_data) + (bfd *, bfd *); + /* Called to set private backend flags. */ + bfd_boolean (*_bfd_set_private_flags) (bfd *, flagword); + + /* Called to print private BFD data. */ + bfd_boolean (*_bfd_print_private_bfd_data) (bfd *, void *); + + /* Core file entry points. */ +#define BFD_JUMP_TABLE_CORE(NAME) \ + NAME##_core_file_failing_command, \ + NAME##_core_file_failing_signal, \ + NAME##_core_file_matches_executable_p + + char * (*_core_file_failing_command) (bfd *); + int (*_core_file_failing_signal) (bfd *); + bfd_boolean (*_core_file_matches_executable_p) (bfd *, bfd *); + + /* Archive entry points. */ +#define BFD_JUMP_TABLE_ARCHIVE(NAME) \ + NAME##_slurp_armap, \ + NAME##_slurp_extended_name_table, \ + NAME##_construct_extended_name_table, \ + NAME##_truncate_arname, \ + NAME##_write_armap, \ + NAME##_read_ar_hdr, \ + NAME##_openr_next_archived_file, \ + NAME##_get_elt_at_index, \ + NAME##_generic_stat_arch_elt, \ + NAME##_update_armap_timestamp + + bfd_boolean (*_bfd_slurp_armap) (bfd *); + bfd_boolean (*_bfd_slurp_extended_name_table) (bfd *); + bfd_boolean (*_bfd_construct_extended_name_table) + (bfd *, char **, bfd_size_type *, const char **); + void (*_bfd_truncate_arname) (bfd *, const char *, char *); + bfd_boolean (*write_armap) + (bfd *, unsigned int, struct orl *, unsigned int, int); + void * (*_bfd_read_ar_hdr_fn) (bfd *); + bfd * (*openr_next_archived_file) (bfd *, bfd *); +#define bfd_get_elt_at_index(b,i) BFD_SEND (b, _bfd_get_elt_at_index, (b,i)) + bfd * (*_bfd_get_elt_at_index) (bfd *, symindex); + int (*_bfd_stat_arch_elt) (bfd *, struct stat *); + bfd_boolean (*_bfd_update_armap_timestamp) (bfd *); + + /* Entry points used for symbols. */ +#define BFD_JUMP_TABLE_SYMBOLS(NAME) \ + NAME##_get_symtab_upper_bound, \ + NAME##_canonicalize_symtab, \ + NAME##_make_empty_symbol, \ + NAME##_print_symbol, \ + NAME##_get_symbol_info, \ + NAME##_bfd_is_local_label_name, \ + NAME##_bfd_is_target_special_symbol, \ + NAME##_get_lineno, \ + NAME##_find_nearest_line, \ + _bfd_generic_find_line, \ + NAME##_find_inliner_info, \ + NAME##_bfd_make_debug_symbol, \ + NAME##_read_minisymbols, \ + NAME##_minisymbol_to_symbol + + long (*_bfd_get_symtab_upper_bound) (bfd *); + long (*_bfd_canonicalize_symtab) + (bfd *, struct bfd_symbol **); + struct bfd_symbol * + (*_bfd_make_empty_symbol) (bfd *); + void (*_bfd_print_symbol) + (bfd *, void *, struct bfd_symbol *, bfd_print_symbol_type); +#define bfd_print_symbol(b,p,s,e) BFD_SEND (b, _bfd_print_symbol, (b,p,s,e)) + void (*_bfd_get_symbol_info) + (bfd *, struct bfd_symbol *, symbol_info *); +#define bfd_get_symbol_info(b,p,e) BFD_SEND (b, _bfd_get_symbol_info, (b,p,e)) + bfd_boolean (*_bfd_is_local_label_name) (bfd *, const char *); + bfd_boolean (*_bfd_is_target_special_symbol) (bfd *, asymbol *); + alent * (*_get_lineno) (bfd *, struct bfd_symbol *); + bfd_boolean (*_bfd_find_nearest_line) + (bfd *, struct bfd_section *, struct bfd_symbol **, bfd_vma, + const char **, const char **, unsigned int *); + bfd_boolean (*_bfd_find_line) + (bfd *, struct bfd_symbol **, struct bfd_symbol *, + const char **, unsigned int *); + bfd_boolean (*_bfd_find_inliner_info) + (bfd *, const char **, const char **, unsigned int *); + /* Back-door to allow format-aware applications to create debug symbols + while using BFD for everything else. Currently used by the assembler + when creating COFF files. */ + asymbol * (*_bfd_make_debug_symbol) + (bfd *, void *, unsigned long size); +#define bfd_read_minisymbols(b, d, m, s) \ + BFD_SEND (b, _read_minisymbols, (b, d, m, s)) + long (*_read_minisymbols) + (bfd *, bfd_boolean, void **, unsigned int *); +#define bfd_minisymbol_to_symbol(b, d, m, f) \ + BFD_SEND (b, _minisymbol_to_symbol, (b, d, m, f)) + asymbol * (*_minisymbol_to_symbol) + (bfd *, bfd_boolean, const void *, asymbol *); + + /* Routines for relocs. */ +#define BFD_JUMP_TABLE_RELOCS(NAME) \ + NAME##_get_reloc_upper_bound, \ + NAME##_canonicalize_reloc, \ + NAME##_bfd_reloc_type_lookup, \ + NAME##_bfd_reloc_name_lookup + + long (*_get_reloc_upper_bound) (bfd *, sec_ptr); + long (*_bfd_canonicalize_reloc) + (bfd *, sec_ptr, arelent **, struct bfd_symbol **); + /* See documentation on reloc types. */ + reloc_howto_type * + (*reloc_type_lookup) (bfd *, bfd_reloc_code_real_type); + reloc_howto_type * + (*reloc_name_lookup) (bfd *, const char *); + + + /* Routines used when writing an object file. */ +#define BFD_JUMP_TABLE_WRITE(NAME) \ + NAME##_set_arch_mach, \ + NAME##_set_section_contents + + bfd_boolean (*_bfd_set_arch_mach) + (bfd *, enum bfd_architecture, unsigned long); + bfd_boolean (*_bfd_set_section_contents) + (bfd *, sec_ptr, const void *, file_ptr, bfd_size_type); + + /* Routines used by the linker. */ +#define BFD_JUMP_TABLE_LINK(NAME) \ + NAME##_sizeof_headers, \ + NAME##_bfd_get_relocated_section_contents, \ + NAME##_bfd_relax_section, \ + NAME##_bfd_link_hash_table_create, \ + NAME##_bfd_link_hash_table_free, \ + NAME##_bfd_link_add_symbols, \ + NAME##_bfd_link_just_syms, \ + NAME##_bfd_final_link, \ + NAME##_bfd_link_split_section, \ + NAME##_bfd_gc_sections, \ + NAME##_bfd_merge_sections, \ + NAME##_bfd_is_group_section, \ + NAME##_bfd_discard_group, \ + NAME##_section_already_linked, \ + NAME##_bfd_define_common_symbol + + int (*_bfd_sizeof_headers) (bfd *, struct bfd_link_info *); + bfd_byte * (*_bfd_get_relocated_section_contents) + (bfd *, struct bfd_link_info *, struct bfd_link_order *, + bfd_byte *, bfd_boolean, struct bfd_symbol **); + + bfd_boolean (*_bfd_relax_section) + (bfd *, struct bfd_section *, struct bfd_link_info *, bfd_boolean *); + + /* Create a hash table for the linker. Different backends store + different information in this table. */ + struct bfd_link_hash_table * + (*_bfd_link_hash_table_create) (bfd *); + + /* Release the memory associated with the linker hash table. */ + void (*_bfd_link_hash_table_free) (struct bfd_link_hash_table *); + + /* Add symbols from this object file into the hash table. */ + bfd_boolean (*_bfd_link_add_symbols) (bfd *, struct bfd_link_info *); + + /* Indicate that we are only retrieving symbol values from this section. */ + void (*_bfd_link_just_syms) (asection *, struct bfd_link_info *); + + /* Do a link based on the link_order structures attached to each + section of the BFD. */ + bfd_boolean (*_bfd_final_link) (bfd *, struct bfd_link_info *); + + /* Should this section be split up into smaller pieces during linking. */ + bfd_boolean (*_bfd_link_split_section) (bfd *, struct bfd_section *); + + /* Remove sections that are not referenced from the output. */ + bfd_boolean (*_bfd_gc_sections) (bfd *, struct bfd_link_info *); + + /* Attempt to merge SEC_MERGE sections. */ + bfd_boolean (*_bfd_merge_sections) (bfd *, struct bfd_link_info *); + + /* Is this section a member of a group? */ + bfd_boolean (*_bfd_is_group_section) (bfd *, const struct bfd_section *); + + /* Discard members of a group. */ + bfd_boolean (*_bfd_discard_group) (bfd *, struct bfd_section *); + + /* Check if SEC has been already linked during a reloceatable or + final link. */ + void (*_section_already_linked) (bfd *, struct bfd_section *, + struct bfd_link_info *); + + /* Define a common symbol. */ + bfd_boolean (*_bfd_define_common_symbol) (bfd *, struct bfd_link_info *, + struct bfd_link_hash_entry *); + + /* Routines to handle dynamic symbols and relocs. */ +#define BFD_JUMP_TABLE_DYNAMIC(NAME) \ + NAME##_get_dynamic_symtab_upper_bound, \ + NAME##_canonicalize_dynamic_symtab, \ + NAME##_get_synthetic_symtab, \ + NAME##_get_dynamic_reloc_upper_bound, \ + NAME##_canonicalize_dynamic_reloc + + /* Get the amount of memory required to hold the dynamic symbols. */ + long (*_bfd_get_dynamic_symtab_upper_bound) (bfd *); + /* Read in the dynamic symbols. */ + long (*_bfd_canonicalize_dynamic_symtab) + (bfd *, struct bfd_symbol **); + /* Create synthetized symbols. */ + long (*_bfd_get_synthetic_symtab) + (bfd *, long, struct bfd_symbol **, long, struct bfd_symbol **, + struct bfd_symbol **); + /* Get the amount of memory required to hold the dynamic relocs. */ + long (*_bfd_get_dynamic_reloc_upper_bound) (bfd *); + /* Read in the dynamic relocs. */ + long (*_bfd_canonicalize_dynamic_reloc) + (bfd *, arelent **, struct bfd_symbol **); + +@end example +A pointer to an alternative bfd_target in case the current one is not +satisfactory. This can happen when the target cpu supports both big +and little endian code, and target chosen by the linker has the wrong +endianness. The function open_output() in ld/ldlang.c uses this field +to find an alternative output format that is suitable. +@example + /* Opposite endian version of this target. */ + const struct bfd_target * alternative_target; + + /* Data for use by back-end routines, which isn't + generic enough to belong in this structure. */ + const void *backend_data; + +@} bfd_target; + +@end example + +@findex bfd_set_default_target +@subsubsection @code{bfd_set_default_target} +@strong{Synopsis} +@example +bfd_boolean bfd_set_default_target (const char *name); +@end example +@strong{Description}@* +Set the default target vector to use when recognizing a BFD. +This takes the name of the target, which may be a BFD target +name or a configuration triplet. + +@findex bfd_find_target +@subsubsection @code{bfd_find_target} +@strong{Synopsis} +@example +const bfd_target *bfd_find_target (const char *target_name, bfd *abfd); +@end example +@strong{Description}@* +Return a pointer to the transfer vector for the object target +named @var{target_name}. If @var{target_name} is @code{NULL}, +choose the one in the environment variable @code{GNUTARGET}; if +that is null or not defined, then choose the first entry in the +target list. Passing in the string "default" or setting the +environment variable to "default" will cause the first entry in +the target list to be returned, and "target_defaulted" will be +set in the BFD if @var{abfd} isn't @code{NULL}. This causes +@code{bfd_check_format} to loop over all the targets to find the +one that matches the file being read. + +@findex bfd_target_list +@subsubsection @code{bfd_target_list} +@strong{Synopsis} +@example +const char ** bfd_target_list (void); +@end example +@strong{Description}@* +Return a freshly malloced NULL-terminated +vector of the names of all the valid BFD targets. Do not +modify the names. + +@findex bfd_seach_for_target +@subsubsection @code{bfd_seach_for_target} +@strong{Synopsis} +@example +const bfd_target *bfd_search_for_target + (int (*search_func) (const bfd_target *, void *), + void *); +@end example +@strong{Description}@* +Return a pointer to the first transfer vector in the list of +transfer vectors maintained by BFD that produces a non-zero +result when passed to the function @var{search_func}. The +parameter @var{data} is passed, unexamined, to the search +function. + |